A Zero-phase-sequence Current Transformer (ZCT) is a device that detects a zero-phase current flowing in an electric power line inserted through its own detection core. A ZCT is used, for example, in switchboards, electrical devices and the like, as a detector that detects a ground-fault current caused by a ground fault.
Patent Documents 1 and 2 are examples of documents that disclose a current detecting apparatus and the like in which a ZCT is used. For example, Patent Document 1 discloses a direct-current ground-fault detecting apparatus that detects a ground fault of a direct current at a low cost with a high level of precision thereby ensuring a high level of safety. Patent Document 2 discloses a direct-current ground-fault current detecting circuit that accurately detects whether a direct-current ground-fault current has generated or accurately detects a direct-current value at a given moment without being influenced by the hysteresis characteristics of a ZCT.
Patent Document 1: Japanese Patent Application Laid-open No. 2004-153991
Patent Document 2: Japanese Patent Application Laid-open No. 2005-065382